The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
Wireless communication systems are constantly under development. Developing systems provide a cost-effective support of high data rates and efficient resource utilization. One communication system under development is the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) Release 8. An improved version of the Long Term Evolution radio access system is called LTE-Advanced (LTE-A). The LTE is designed to support various services, such as high-speed data, multimedia unicast and multimedia broadcast services.
In addition to cellular operation, in most systems direct device-to-device communication is possible. In current methods for device-to-device communication, low power technologies such as Bluetooth or Wireless Local Area Networks (WLAN) have been used. In these solutions, the communication is totally independent of the communication infrastructure and is usually based on users being in line of sight with each other. In networks designed for use by government agencies and emergency services, such as Tetra (Terrestrial trunked radio), device-to-device communication has been implemented but those solutions are not suitable for use in general communication networks.
As certain frequency bands (so-called White Spaces) are proposed to be reserved for non-cellular radio use there is a need for realizing device-to-device communication having a longer range than the line of sight. The development of such solution faces several challenges. For example, the solution should be able to work without causing interference to cellular operation and allow minimizing of extra device power consumption.